Heavy ceramic shaped material, process for the production thereof and the use thereof

Abstract

Heavy ceramic shaped material with a content of at least one of the components magnesia, fired dolomite, chromite and spinel, characterized by a microcrack system substantially homogeneously distributed in the shaped material structure, as well as process for producing such a heavy ceramic shaped material and the use thereof.

We claim: 
     
       1. A coarse sintered and calcined ceramic shaped body consisting essentially of at least one of the constituents magnesium oxide, fired dolomite, chromite and spinel comprising a micro-crack system substantially uniformly distributed in said shaped body, said micro-crack system resulting from the addition, prior to calcining of the entire mixture, of 0.5 to 10 weight percent of a micro-crack initiator having a grain size of 0.1 to 3.0 mm, said micro-crack initiator comprising at least one spinel forming agent which forms a spinel of the system R 2+  O.R 2   3+  O 3  during calcining, R 2+   being Mg, Fe, or mixtures thereof and R 2   3+   being Al, Cr, Fe or mixtures thereof. 
     
     
       2. A shaped body according to claim 1 wherein the proportions of R 2+  O to R 2   3+  O 3  are such that the resulting spinel constitutes at least 75% by weight of the micro-crack initiator. 
     
     
       3. A shaped body according to claim 1 wherein said shaped body contains from 5 to 8 percent by weight of said micro-crack initiator. 
     
     
       4. A shaped body according to claim 1 wherein said micro-crack initiator has a grain size of 0.1 to 1 mm. 
     
     
       5. A shaped body according to claim 1 wherein said micro-crack initiator has a grain size of 0.1 to 0.5 mm. 
     
     
       6. A refractory ceramic brick composed of the shaped body of claim 1.